1. Field of the Invention
This invention relates to a maximum voltage detecting apparatus, and more particularly to such apparatus for detecting the maximum output voltage of an equipment, which generates a potential, such as a light sensor, a heat sensor or a pressure sensor with no power source.
2. Description of the Related Art
A light sensor, a heat sensor, a pressure sensor or a wind sensor generates a potential corresponding to the amount of light, heat or pressure. It is well known in the art to use a comparator 10 such as shown in FIG. 1 of the accompanying drawings for monitoring whether or not the potential exceeds a predetermined value. The comparator 10 usually includes a current mirror circuit 10a and a differentiation circuit 10b. A voltage corresponding to the difference between a non-inverted input terminal and an inverted input terminal is used as the output. A means for generating the potential such as of the light sensor or heat sensor is connected to the non-inverted input terminal, and a reference voltage is applied to the inverted input terminal, so that it is monitored whether the external voltage such as of the light sensor or heat sensor exceeds the reference voltage.
However, the conventional voltage measuring means such as a comparator cannot be operative until an external voltage is supplied from a power source 10c. Further, to monitor a maximum voltage all the time, an external memory has to be connected with the output terminal of the comparator to store the output thereof.